Apparatus for coating by electrostatic force



April 17, 1956 T. LINDQUIST 2,742,018

APPARATUS FOR COATING BY ELECTROSTATIC FORCE Filed Jan. 2, 1952 2 ShQets-Sheel 1 April 17, 1956 LINDQUIST 2,742,018

APPARATUS FOR COATING BY ELECTROSTATIC FORCE Filed Jan. 2, 1952 2 Sheets-Sheet 2 partly produced by electrostatic means.

United States PatentO APPARATUS FOR COATING BY ELECTROSTATIC FORCE I '..This invention relates to a method of and apparatus for applying to an adhesively coated surface, a coating comprisingparticles andmore particularly, though not limited to, particles having definite electrostatic axes,

that is, axes in line with the direction of flight of such,

particles when controlled by the attracting and repelling forces of opposed and like electrostatic fields. In the case 2 Y I the particles will be secured with sharp points outwardly projecting. Should the particles have no electrostatic axes, they may still be propelled by the mechanism but they would not be orientated in any particular manner.

The method and mechanism by which such particles of flock or abrasive materials, or the like, may be so orientated and projected will be understood from a description of the flocking machine shown herein; As shown best in Figures 1 and 2, this machine comprises a suitable frame 1 having horizontally spaced pulleys 2 and 3 over whichis passed'a traveling belt supported at its upper stretch 5 by an electro-conductive table 4.

of particles such as fiockwhich comprises fibers of substantially greater length than thickness, these axes will coincide with length.

In the case of sharp particles such axes will pass'through the sharpest points where the greatest concentration of electrostatic charges under the influence of such fields occurs. Ithas for one object to deposit such particles with such axes predominantly perpendicular to the surface to which they are applied, the orientation of the particles and their flight toward the adhesively coated surface being controlled and at least The particles become charged and are orientated and propelled toward the oppositely charged adhesive coated sheet material below by thedischarge or corona from the fiber ends or the sharp points ofthe particles, and by-the repulsion from neighboring like charged particles andelectrodes. For a more'complete understanding of this invention reference may be had to the accompanying drawings in whichi r Figure 1 is'a side'elevation of a two-stage flocking machine embodying the invention.

. Figure 2 is an end elevation of the same.

4 Figure. 3 is 'adetail sectional view to an enlarged scale on line 3,-37of Figure 2. i

U Figure 4 is. a detail sectional view on line 4-4 of .Figure 3. 1

Figure 51 is a diagrammatic view showingatwo stages 0fthe apparatus. i

. I Figure 6 is asectional view on line 6-6 of Figure 5 to a larger scale. 6

. Figure 7 is a view similar to Figure .5, but showing a five-stage machine. I a

t This invention will bepartic'ularly described with relation to a machine for. applying flock to adhesively coated sheet material. This adhesive'may be applied in desired "areas'so that thefioek which is propelled thereagainst will adhere to those areas only to which the adhesive has been applied. Thus desitedpatterns of flock surface may be produced.

It is also-evident that by applyingadhesive to diflerent areas of the sheet material at diiferent times and applying flock of different colors tothese separately coated areas,

desirable ornamental color pattern effects may be produced,'the flock fibers being attached-endwise to the coated :surface and thus presenting the desirable appearance characteristic of iplush, or like pile fabric.

It will be understood, however, that any particles which have definite electrostatic axes may "be treated in a similat-way and be orientated similarly to flock and bepro- *jected against an adhesive coated surface to which it is desired to attach such particles. With abrasive particles,

insulating end plates 26 'on the base sheet material to which the coating is to be applied and this base sheet material may have desired areas of its upper face precoated with an adhesive which is in tacky condition when the flock or other coating is to be applied.

Above the top stretch 5 of this belt are arranged transverse to the direction of travel of the belt, one or more pairs of electrodes 6. 'As shown best in Figure 3, these electrodes may well be formedas metal tubes and they may be supported and attached to hangers 7 of insulating material provided at their upper end portions with longitudinal slots 8 through which may be extended clamping screws 9. These hangers 7 are thus angularly and axially adjustable on the clamp screws 9, and these screws may be provided with wing nuts 10 to facilitate loosening the hangers 7 for such adjustment as may from time to time be desired, after which they may be tightened to secure the parts in adjusted position.

Above and between each pair of electrodes 6 there is arranged a downwardly bowed foraminous conductive baflle 15. Where flock is to be handled, for example, this bafi le may comprise a screen or foraminous member which may well be of brass. This lower bafile 15 is shown as carried by'a pair of end plates 16 of insulating material having upward extensions 17 slotted as at 18 for the reception of clamping bolts 19 each having a wing nut 20 on its Outer end as shown best in Figure 4.

' Above the baffle 15 there is positioned a flock load retainer formed as a conductive'baflle 25 which may be constructed like the'baflle 15 and likewise be carried'by having slots at 27 (see Figure 4) also engaged by the clamping bolts 19. A longitudinal frame member 28 may support the clamp bolts 19 and an insulating washer 29 may be inserted between the supporting plates 16 and 26. The traveling belt 4 may be driven as by a motor 30 which may be suitably connected thereto as through a reduction gear unit 31 and a chain drive 32, and supply hoppers 35 fo'rthe flock or other material to be deposited may be positioned above the upper bafiles 25. So long as a supply of flock is present on the load retaining bafiles 25 flock is fed therefrom continuously by the electrostatic action and without requiring any mechanical sitting or agitation. The supply hoppers may havesuitable means for agitating and sifting down onto the upper bathe plates the particles contained therein and these distributing hoppers may be driven intermittently whenever the load retainer baffles 25 needto be replenished, as through the chain connections 36, 37, "and 38 and the clutch 39 from the motor 30. As such supply hoppers and their agitating and feeding means are well known in the art, no detail description thereof is given herein, it being sufiicientto state that the flock or other particles are sifted down as desired onto the upper bafiles 25. These baifles, the electrodes 6, and the adhesively coated sheet-material are electrostatically charged, the relationships of these charges being shown in Figure 5.

While the specific charges, whether positive or negative, for each element, are not important, the polarity .is, the material to be coated and the lower bafiie plate are charged to the same polarity and the electrodes 6 .and the upper baffle 25 are charged in the opposite polarity.

Means for statically charging the various parts, and indicated in Figures 1 and 2 as contained in a casing 50 is well known and may, for example, comprise a type known as brute force D. C. power. Another comprises the-R. F. or radio frequency apparatus such as are commonly used in projection television. A D. C. power supply designed to deliver, say, 30 kv. with a capacity of 1 milliamp is quite satisfactory. An R. P. type of power supply producing 24 /2 kv. with a capacity of 200 microamps is also satisfactory. The precise potential provided is not critical, however, but should be sufficient to produce the desired propelling effect and a range of, say, 25 kv. to 45 lav. will ordinarily be found perfectly satisfactory.

Where flock is employed as the coating material, it isimportant that it be in fairly moist condition, as under these conditions it is more easily electrostatically charged and discharged. A moisture content of, say, 10.5% to 13% is satisfactory. This moisture content may be maintained by storing the flock supply under humid conditions at a temperature of 70 F. and a relative humidity of 65%. Rayon flock under such conditions picks up and retains the desired moisture percentage over night. The amount of moisture determines somewhat the best adjustment of the electrodes 6 and the bafiies 15 and 25. Sidewise adjustment of the electrodes 6 varies the volume of flock delivered to the adhesive, and where the flock is to be applied in two or more stages, it is usually found desirable to produce a relatively light coverage at the first stage with increasing volume at each successive point of delivery Decrease in the gap between the electrodes 6 increases the projecting force exerted on the flock. The best relative positioning for the electrodes 6 and the baffles 15 and 25 is dependent upon the length of the, fibers and upon their moisture content and it may be adjusted as the functioning of the apparatus appears to indicate desirable. It will be understood that the various parts, including electrodes and baffles are provided with insulat ing mountings so that they may be oppositely charged as r described.

The effects of the charges on the flock may be understood by an inspection of Figures 5 and 6. Assuming that the various elements are charged as shown, the

upper bafiles 25 being charged negatively, the lower baffies positively, the electrodes 6 negatively, and the sheet material to be coated positively, the flock material retained by the upper bafiies 25 becomes negatively charged and is attracted by the positively charged baffie 15 below. Since the openings through the bafiles are much larger than the fibers, the fibers pass through the upper baffles 25 and are forced by electrostatic attraction toward the oppositely charged lower bafiies 15. The charged fibers orient themselves lengthwise in their direction of flight by repulsion from each other. As the fibers thus projected and orientated lengthwise pass into the field of the lower baffles 15 their charges become reversed in polarity so that as they pass through the lower baffles they are attracted to and between the pairs of electrodes 6. As these electrodes are charged oppositely to the flock particles but in the same polarity as each other, the particles are driven between them where they again change polarity to negative and are repelled by the negatively charged electrodes 6 and attracted to the positively charged adhesively coated sheet material.

Thus the particles are not only projected by gravity, but are also propelled by the reaction of their static charges and the charged parts of the apparatus through the upper and lower bafiles, gaining momentum all the time, and between the electrodes 6. They then strike end on against the adhesively coated sheet material and become firmly embedded in the adhesive while arranged in vertical position. I

In Figure 5 it will be noted that there are two stages of delivery. It is found, however, that these stages may be increased in number by the interposition of other electrodes as 40 which may be interposed between adjacent edges of the lower bafiles 15 'as shown in Figure 7, these electrodes 40 being charged with the-same polarity as the bafiies 15 and the adhesively coated sheet material. The paths of the fiock materials are then somewhat as indicated diagrammatically in Figure 7, particles upon the upper bafllcs 25 being attracted by the electrodes 40, from which they are projected downwardly between these electrodes 44) and the lower baffles 15 in the manner somewhat similar to the manner in which the particles are projected between the adjacent lower electrodes 6. These particles, being then charged with the same polarity as the electrodes 40 are repelled therefrom toward the oppositely charged electrodes 6 and are then changed in polarity and projected against the adhesively coated surface. Thus with the three sets of upper and lower bafiles and three pairs of electrodes 6, the number of delivery positions or stages is increased from three to five by the addition of the upper electrodes 40.

It is also desirable to bridge across the upper bafiies 25 so that the material supplied by the hoppers does not build up on the electrodes 40, and cover plates 41 for this purpose are illustrated in Figure 8. i

From the foregoing description of certain embodiments of this invention and the method of operation, it should be evident to those skilled in the art that various changes and modifications may be made without departing from the spirit or scope of the invention.

I claim:

1. A machine of the class described, comprising a traveling belt for transporting through an electrostatic field sheet material provided with an adhesive coated top surface, an electro-conductive table supporting said belt, a pair of electrodes arranged above and Itransverse to the line of travel of said belt, a pair of downwardly bowed foraminous baifies each having openings larger than the particles to be handled, and arranged one above the other in the space between said electrodes, means for electrostatically charging said table and the lower of said baffies to one polarity and said electrodes and the upper of said baffles to the opposite polarity, the upper of said baffles serving as a load retainer of such particles fed by electrostatic force to said coated surface.

2. A machine of the class described, comprising a traveling belt for transporting through an electrostatic field sheet material provided with an adhesive coated top surface, an electro-conductive table supporting said belt, a pair of electrodes arranged above and transverse to the line of travel of said belt, a pair of downwardly bowed foraminous baffles each having openings larger than the particles to be handled, and arranged one above the other above the space between said electrodes, means for electrostatically charging said table and the lower of said battles to one polarity and said electrodes and the upper of said bafiles to the opposite polarity, the upper of said baflies serving as a load retainer of such particles fed by electrostatic force to said coated surface, said electrodes being mounted for adjustment toward and from each other, and said bafiies being mounted for vertical adjustment.

3. A machine of the class described, comprising a traveling belt for transporting through an electrostatic field sheet material provided with an adhesive coated top surface, an electro-conductive table supporting said belt, a pair of electrodes arranged above and transverse to the line of travel of said belt, a pair of downwardly bowed foraminous baffles each having openings larger than the particles to be handled, and arranged one above the other in the space between said electrodes, means for electrostatically charging said table and the lower of said baffles to one polarity and said electrodes and the upper of said baffies to the opposite polarity, the upper of said baffles serving as a load retainer of such particles fed by electrostatic force to said coated surface, and means for applying such particles to the upper of said bafiies.

4. A machine of the class described, comprising a traveling belt for transporting through an electrostatic field sheet material provided with an adhesive coated top surface, an electro-conductive table supporting said belt, a series of pairs of electrodes arranged transverse to the line of travel of said belt and spaced apart above said belt, a pair of downwardly bowed foraminous bafiles each having openings larger than the particles to be handled, and arranged one above the other in the spaces between adjacent pairs of said electrodes, means for electrostatically charging said table and the lower of said baffles to onepolarity and said electrodes and the upper of said battles to the opposite polarity, the upper of said baflies serving as a load retainer of such particles fed by electrostatic force to said surface, imperforate plates bridging over adjacent edges of said upper baflles, and a second set of laterally extending electrodes arranged adjacent to edges of said lower baffies and charged to the polarity of said lower baffles References Cited in the file of this patent UNITED STATES PATENTS 653,343 Gates July 10, 1900 668,792 Blake et a1. Feb. 26, 1901 1,549,875 Home Aug. 18, 1925 2,027,308 Schacht Jan. 7, 1936 2,128,907 Benner et al Sept. 6, 1938 2,152,077 Meston et a1 Mar. 28, 1939 2,173,032 Wintermute Sept. 12, 1939 2,174,328 Meston et al. Sept. 26, 1939 2,246,253 Johnson M June 17, 1941 2,248,064 Carlton et al July 8, 1941 2,287,837 Smyser June 30, 1942 2,328,904 Hiers Sept. 7, 1943 2,447,374 Smyser Aug. 17, 1948 2,527,501 Saks Oct. 24, 1950 

1. A MACHINE OF THE CLASS DESCRIBED, COMPRISING A TRAVELING BELT FOR TRANSPORTING THROUGH AN ELECTROSTATIC FIELD SHEET MATERIAL PROVIDED WITH AN ADHESIVE COATED TOP SURFACE, AN ELECTRO-CONDUCTIVE TABLE SUPPORTING SAID BELT, A PAIR OF ELECTRODES ARRANGED ABOVE AND TRANSVERSE TO THE LINE OF TRAVEL OF SAID BELT, A PAIR OF DOWNWARDLY BOWED FORAMINOUS BAFFLES EACH HAVING OPENINGS LARGER THAN THE PARTICLES TO BE HANDLED, AND ARRANGED ONE ABOVE THE OTHER IN THE SPACE BETWEEN SAID ELECTRODES, MEANS FOR ELECTROSTATICALLY CHARGING SAID TABLE AND THE LOWER OF SAID BAFFLES TO ONE POLARITY AND SID ELECTRODES AND THE UPPER OF SAID BAFFLES TO THE OPPOSITE POLARITY, THE UPPER OF SAID BAFFLES SERVING AS A LOAD RETAINER OF SUCH PARTICLES FED BY ELECTROSTATIC FORCE TO SAID COATED SURFACE. 